1. Field of the Invention
The invention relates to an air bed having a plurality of air chambers arranged in series, each of the air chambers being expanded by introducing air thereinto when in use.
2. Description of the Prior Art
FIG. 1 illustrates one conventional air bed. The illustrated air bed 1 includes five air chambers 1a, 1b, 1c, 1d and 1e arranged in series and composed of air-impermeable sheet. The five air chambers 1a to 1e have an elongated shape approximately square in cross section, and are the same in size. Though not illustrated, each of the air chambers 1a to 1e has a length in a direction perpendicular to a plane of the drawing.
One of the five air chambers 1a to 1e, for instance, the air chamber 1b is connected to an air pump 2. The air pump 2 feeds compressed air into the air chamber 1b. An electric power supply 3 is electrically connected to the air pump 2, and supplies electric power to the air pump 2 for its operation. The air pump 2 is connected further to a controller 4 which controls an on/off state of the air pump 2.
The air chamber 1b is formed with two pressure governing valves 5. Each of the air chambers 1a and 1c situated adjacent to the air chamber 1b is formed with a three-way valve 6. The air chambers 1a and 1c are in gas communication with the air chamber 1b through the gas governing valves 5 and the three-way valves 6. Similarly, the air chamber 1c is in gas communication with the air chamber 1d through the gas governing valve 5 and the three-way valve 6, and the air chamber 1d is in gas communication with the air chamber 1e through the gas governing valve 5 and the three-way valve 6.
Each of the air chambers 1a and 1e situated at opposite ends of the air bed 1 is formed with an exhaust port 7 through which compressed air existing in the air chambers 1a and 1e gradually leaks.
The conventional air bed illustrated in FIG. 1 is used as follows.
First, the controller 4 starts the air pump 2 to operate to thereby feed compressed air into the air chamber 1b. The pressure governing valves 5 are normally closed, but are open when an ambient pressure exceeds a predetermined pressure. Hence, when an internal pressure of the air chamber 1b is over the predetermined pressure, the pressure governing valve 5 is open. As a result, compressed air existing in the air chamber 1b is fed into the air chambers 1a and 1c situated adjacent to the air chamber 1b, through the three-way valves 6 of the air chambers 1a and 1c.
The compressed air is fed into the air chamber 1d, and then into the air chamber 1e in the same manner.
In the above-mentioned way, each of the air chambers 1a to 1e has a predetermined internal pressure, and as a result, is expanded to a certain size. Thus, the air bed 1 can be used as a bed.
Even after each of the air chambers 1a to 1e has acquired a predetermined internal pressure, the air pump 2 is kept operating. Extra compressed air leaks to the atmosphere through the exhaust ports 7 formed at the air chambers 1a and 1e. By always flowing air through the air chambers, it would be possible to avoid moisture from staying in the air chambers 1a to 1e.
In general, a head, a body, arms and legs of a man are different in weight. Hence, when a man lies on an air bed, different loads are exerted on the air chambers 1a to 1e. For instance, since a body of a man is heavier than legs, a load exerted on an air chamber on which a body of a man lies is greater than a load exerted on an air chamber on which legs of a man lie.
Hence, since different loads are exerted on the air chambers, it would be necessary to control a volume of compressed air to be fed into each of the air chambers, in accordance with a load exerted on the air chambers.
However, the compressed air is fed only to the air chamber 1b among the five air chambers 1a to 1e, and then is supplied to the other chambers 1a, 1c, 1d and 1e from the air chamber 1b in the conventional air bed 1 illustrated in FIG. 1. Accordingly, it would be quite difficult or almost impossible to control a volume of Compressed air to be fed into each of the air chambers to thereby control an internal pressure of each of the air chambers 1a to 1e.
In addition, the compressed air is fed into the air chambers 1a, 1c, 1d and 1e from the air chamber 1b one by one in the conventional air bed 1 illustrated in FIG. 1. Hence, it takes much time to fill all the air chambers 1a to 1e with compressed air. This means that the conventional air bed is not available for emerging uses requiring fast filling and more precise control.